EUV Litho Still a Work in Progress

Despite progress in recent months, the semiconductor industry remains anxious about the development of extreme ultraviolet lithography.

As has been the case for the past several years, trepidation over the development of extreme ultraviolet (EUV) lithography was one of the oft-repeated themes at this year's Semicon West fab tool tradeshow in San Francisco.

"EUV is the highest priority for our industry," said Luc Van den Hove, president and CEO of European microelectronics research institute Imec, in a panel discussion at the event.

In May, Dutch lithography vendor ASML finalized a deal to acquire lithography source vendor Cymer for about $2.6 billion. The deal is largely considered an attempt by ASML to take a firmer hand in the development of an EUV source. Cymer is one of three developers trying to create a source that would be powerful enough to support commercial production throughput of an EUV lithography tool.

In February, at the SPIE Advanced Lithography Conference, ASML showed data indicating that it had raised the maximum power on its power source to 55 watts. Ryan Young, a spokesman for ASML, said this week that 55 watts would be enough to support EUV tool throughput of about 43 wafers per hour.

More significant, according to Young, is that ASML has shown the power source can support a maximum power of 50 watts for long periods of time.

Young also noted that the development work is being done on ASML's pre-production EUV machine, the NXE:3100. When ASML transfers the source to its NXE:3300 EUV tool, which has a larger drive laser, the 50 watts will become 80 watts, enough to support throughput of more than 60 wafers per hour.

Young added that improving source power -- while the most significant stumbling block to putting EUV in production -- is only one place where ASML needs to make progress. ASML will continue working on improving the raw power of the source, but also focus on other needed improvements in the power source around availability and dose control.

ASML's latest goal is to be able to support a throughput of about 70 wafers per hour sometime in 2014. (See: ASML says fast EUV machines coming by 2016.) According to Young, that's roughly the throughput threshold that most customers say would make it worthwhile to adopt EUV. "But every customer's process is different," he added.

The original plan was for EUV to be in production years ago, but development hiccups have pushed out the technology multiple times. ASML has six pre-production EUV development tools currently in the field.

Intel -- which last year acquired a 15 percent stake in ASML and ponied up additional funds specifically for the development of EUV in a deal worth a total of $4.1 billion -- has been hoping to deploy EUV lithography at the 10 nm node in the second half of 2015. (See: Intel buys stake in ASML to boost 450-mm, EUV R&D.) Intel also said it would be prepared to extend optical immersion lithography to that node in the event that EUV is not ready. Samsung and TSMC have entered into similar deals with ASML.

Ludo Deferm, executive vice president of business development at Imec, said this week that extending optical immersion to that node may not be economically feasible. Because extending optical immersion to 10 nm could require three or more exposures -- and thus three or more photomasks for critical layers -- the costs involved would increase exponentially.

But Deferm told us Imec is confident that EUV will eventually be put in production. "We are confident that it will come," he said. "I don't have a crystal ball, either. We can't predict the future."

This seems like an old story, I know. The development of EUV lithography has been painfully slow. But it does seem like they are getting there, slowly but surely. The industry is really depending on EUV.

Yes, the technical side of EUV lithography seems to be making slow but steady progress. However, the cost side of EUV litho will take much longer. Eventhough it might become less expensive than quadruple patterning using immersion 193 nm lithography, it will still be prohibitively expensive for most applications for several more years.

It's probably going to be a while. I should have mentioned in this posting, too, that the power source is the big issue, but there are still otherss. Since the masks will have no pellicle (they have discovered a material that is transmissive enough), mask defects and mask cleaning are a couple big issues to solve. And right now nobody knows how long the masks will last. (IMEC does have a research program going on finding ways to clean the EUV masks).

EUV has been under development since 2006 and most of the foundries do not expect EUV until at least the 7nm generation, one generation beyond the 10nm Intel mentioned. That demonstrates the challenge in bringing this technology to an economic level. However, what really concerns me is now the entire industry is betting on the success of one company ASML/Cymer. I can't remember a time in the history of this industry that so much relied on one technology and one company. And even with EUV, we are likely to hit other physical limits at or just beyond th 5nm limitation. Gordon Moore has predicted the end of his own law three times that I am aware of and the last time was rather recent. He may br right this time around.

This year at SPIE, the troubles with higher doses and higher numerical apertures were pointed out. The more advanced nodes are even harder for EUV to get in. Fortunately it was also revealed 10 nm multi-patterning may not need multiple optical immersion exposures.

Why this guys taking so much time to complete this, they should have done by now...you know once I have seen a guy who done with an <a href="http://www.aiglemed.com/mobility-aid/">Powered wheelchairs</a> project within a week.

A comment was made above that EUV has been under development since 2006. I suggest readers google SXPL (soft x-ray projection lithography) and find papers in the early 1990s and even late 1980s. Some marketing guy changed it's name from SXPL to EUV so it would sound more like DUV, but it didnt seem to change the wavelength. X-ray lithography is just as challenging now as it was then, after huge expenditure of money and manpower. Mr. McGrath's title "a work in progress" is an understatement. The interesting question is why. It's not as if alternatives don't exist.

There are alternatives. Immersion with multiple passes, direct write, and a few other technologies. But other than the multi-pass immersion, my understanding is that all of these other technologeis are also still in development. And each has its own limitations. My understanding from talking with people about this through the years is that most people that are involved in lithography see EUV as the best hope, even though the kidns are still being worked out (and probably will be being worked out for years).